The present invention relates to a yaw rate sensor, and more specifically, a yaw rate sensor that detects the yaw rate of two perpendicular axes and a method for manufacturing the sensor.
Tuning fork or vibration ring type sensors are conventionally known as yaw rate sensors. The tuning fork or the vibration ring type yaw rate sensors are made of many parts. The yaw rate sensors detect the angular velocity and the rotation direction around one axis.
There is a need for a two-axis yaw rate sensor that simultaneously detects the angular velocities and rotation directions of X and Y axes, which cross one another at a right angle. However, combining two sensors, each of which detects the angular velocity and the rotation of one axis, complicates the structure of the yaw rate sensor. This increases the number of parts and the manufacturing costs of the yaw rate sensor.
An objective of the present invention is to provide a simple two-axis yaw rate sensor and its manufacturing method.
To achieve the above objective, a two-axis yaw rate sensor according to the present invention includes: a ring-shaped member (15); wherein the ring-shaped member (15) includes first to fourth vibrating drive surfaces (16a-16d) located in turn in a circumferential direction and support parts (17) located between the adjacent drive surfaces (16a-1c), wherein the first and the third drive surfaces (16a, 16c) are opposed to one another on a first axis passing through the center of the ring-shaped member (15), the second and the fourth drive surfaces (16b, 16d) are substantially perpendicular to the first axis and oppose one another on a second axis passing through the center of the ring-shaped member (15); a support member (11) for supporting the ring-shaped member (15) at each support part (17); a piezoelectric member (18), which is located on each drive surface (16a-16d) and vibrates the corresponding drive surface (16a-16d) in a radial direction of the ring-shaped member (15); a coupling portion (22) extending from each drive surface (16a-16d); a weight (21), which is coupled to each coupling portion (22) and swings in a direction substantially perpendicular to the vibrating direction of the drive surfaces (16a-16d); and a deformation detection member (24a-24d) formed on each coupling portion (22) for detecting the deformation of the corresponding coupling portion (22).
A method for manufacturing a yaw rate sensor of the present invention includes: forming a ring-shaped member (15) by punching a flat metal plate, a weight integrally coupled to the ring-shaped member (15), and a coupling portion (22) coupling the ring-shaped member (15) to the weight (21); bending the ring shaped member (15) to be cylindrical; bending the coupling portion (22) such that the weight (21) extends perpendicular to the peripheral or inner surface of the ring-shaped member (15); forming a titanium film on the inner and peripheral surfaces and on the coupling portion (22) of the weight (21); forming a piezoelectric film (18) on the titanium film; and forming an electrode (19a-19d, 24a, 24d) on the piezoelectric film (18) corresponding to the ring-shaped member (15) and on the piezoelectric film (18) of the coupling portion (22).